Midway through the third quarter of an April 2 NBA game between the Cleveland Cavaliers and Washington Wizards, a Cleveland guard tossed a lob pass toward the rim. Most of us sitting in the Verizon Center, in downtown Washington, D.C., had an idea what was about to happen.

Lebron James, the 24-year-old heir apparent to the NBA’s Best Ever moniker, elevated from the left baseline, caught the pass and, as he floated through the lane like a bird on wing, dunked the ball behind his head. The crowd roared its appreciation and even some of the Wizards’ players nodded in approval.

But the theatrical dunk, which came at a point when Cleveland was trailing by double digits, was one of only a small handful of highlights James – the leading candidate for league MVP for the 2008-2009 NBA season – had produced to that point in the contest.

He spent a good portion of his on-court minutes on the periphery, loping up and down the court with little urgency, distributing passes and setting an occasional pick but otherwise leaving the driving and scoring burden to his teammates.

The Wizards held on to win, despite a late flourish by James that left him with 31 “quiet” points.

The outcome hardly mattered: The Wizards were nearing a merciful end to a season that tied the franchise’s worst-ever record. The Cavaliers had all but wrapped up the top seed in the Eastern Conference for the playoffs.

Loafing or saving energy?

But from a health perspective, the on/off performance of James raised a question: How is it that NBA players – and many other professional athletes – are able to switch gears so readily and (seemingly) with few physical repercussions? How can someone go “half speed” without risking injury and still appear competitive on a court with some of the world’s best athletes?

DeNubile made an important distinction between going half-speed and being tentative. If you’re tentative – in any sport at any time – that’s when you risk injury.

“You need to be relaxed,” DeNubile said, to ensure that all of your faculties are there when you need them (for example, to leap to the rafters of an arena and throw down a reverse dunk). But “relaxed” doesn’t mean you’re not ready to go full speed on a moment’s notice. It’s similar to the difference between a cat stalking prey (relaxed but alert and focused, ready to strike) and a skier standing atop a cliff, doubting that he can navigate the leap (frightened and tense, and becoming increasingly less focused). Skilled athletes can go partial speed and still stay relaxed, DeNubile notes.

But this doesn’t apply to all sports. Diving, for example, or pitching a baseball require a focused anaerobic punch that would be very difficult to perform lackadaisically.

Why players hold back

For NBA players, the decision to occasionally temper their effort is not always bad.

“Recovery is so important for the players [and] metabolic recovery can vary from athlete to athlete,” DeNubile said.

“A lot of players come into the season three-quarters fit and use the season to get in shape for the playoffs. You’re better off if you come into the season fit,” but in an 82-game season even some of the fittest players have low-intensity nights. They may do it for selfish reasons – a contract dispute, for example. But in most cases they do it because they have to keep some reserves in the tank to stay competitive throughout a season that, for playoff teams, can span almost three-quarters of the year.

“When we went to finals some players were dangerously over-trained,” he explained. “We did blood work [on the team] and you could see the guys who were on the brink. When you push too hard the body can start to break down. It’s the reverse effect” of training well.

DeNubile didn’t name players who were over-trained but he did cite Allen Iverson as one player who rarely gives reduced effort. “Every game of the year he’s giving 100 percent, 150 percent, diving for loose balls, playing as hard as he can,” DeNubile said. “That guy is incredible. He just doesn’t have an off switch.”

Somehow Iverson has stayed competitive for 12 (and counting) NBA seasons, defying predictions from many analysts that his all-out, physical style of play would result in a truncated career.

Are you over training?

Most of us will never play professional sports. But that doesn’t mean we can’t learn from those who do.

While the great majority of Americans is in no danger of over training (see: obesity epidemic, 21st century), some of us become addicted to strenuous exercise and tend to push ourselves harder than we should. One easy marker to check for over-training is your resting heart rate. Check it in the morning, right after you wake up, DeNubile says. (If you fear you are already over-trained, take a week off and see if that morning heart rate drops by 10 to 15 percent; if yes, you were likely over-training.)

Most are NBA players are incredibly fit and have resting heart rates around 60 beats-per-minute.

“When you see it start to bump up 10 beats per minute, that’s one of the signs over overtraining,” he says. “Or if a player says he’s getting a good night’s sleep but is still feeling tired.”

This made me wonder how much fuel NBA players burn during a game.

Interestingly, they’re burning about the same number of calories – 10 to 12 calories per minute – as you or I would during vigorous exercise. But because they are so fit their bodies use available energy stores much more efficiently than would a less-fit body, and thus they can accomplish more physically with less energy.

But DeNubile says that doesn’t make NBA players immune to basic exercise risks. “It can get dangerous when you’re tank starts to get low. People who sweat big can get dehydrated. You’ll see a player come off [the court] and he’s not happy about how he was playing or whatever and the trainer will offer him water or Gatorade and he’ll wave it off. That always worries me.”

These guys need to replenish lost fluid just like the rest of us. It’s nice to know we have at least that in common.

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